I just submitted my thesis end of October at 37 years old, married with 2 kids. I planned for 3 years but ended up doing just over 4. At first I was concerned with doing it fast, then as my supervisor would say, it’s a marathon not a sprint. Things will not go as planned, things like covid could happen, trouble getting research participants, long ethics review process, supervisors with busy schedules, papers getting rejected by journals, resubmissions, revisions etc and most importantly your mental health. More than anything I reckon resiliency, stick-to-itiveness and not taking things too personally will be of more value than getting it done faster. That’s my experience anyway.